1. Field of the Invention
The present invention relates to an image forming apparatus such as an electro-photographic copying machine or a laser beam printer, and more particularly to a system for supporting a photoconductor drum and a development sleeve.
2. Related Background Art
A conventional image forming apparatus is provided with a development roller including a development sleeve and a magnet roller, and a periphery of the development roller is constructed as shown in FIG. 7, in which numeral 101 denotes a photoconductor drum, numeral 102 denotes a photoconductor drum gear, numeral 103 denotes a development sleeve, numeral 104 denotes a development roller flange, numeral 105 denotes a magnet roller, numeral 106 denotes a holder, numeral 107 denotes a development roller bearing, numeral 108 denotes a development roller gear and numeral 109 denotes a spacer roll.
As shown in FIG. 7, the development sleeve 103 has the magnet roller 105 therein and it is supported by the development roller bearing 107 at the opposite ends. The development roller bearing 107 is positioned and fixed to the holder 106 by a positioning pin and a hole (both not shown). The magnet roller 105 is fitted to and held by the holder 106. A photoconductor 101a and a gear 102 are coupled by adhesive, and the photoconductor drum 101 is press-contacted with the development roller by the spring 110 through the spacer roll 109, which functions for keeping a constant spacing between the development roller and the photoconductor drum 101. The photoconductor drum 101 thus constructed receives a rotational driving force from the image forming apparatus main unit through the gear 102 and transmits the driving force to the development roller gear 108 to rotationally drive the development roller in a direction of an arrow.
In such an apparatus, the flange 104 is loosely fitted to an end of the development sleeve 103 as shown in FIG. 8 and they are coupled by adhesive 111. Specifically, the adhesive 111 is applied with a uniform thickness to the entire inner surface of the end of the development sleeve 103 into to which the flange 104 is to be inserted, and then the flange 104 is fitted thereto. Thereafter, it is preserved with keeping the temperature and the humidity constant until the adhesive is completely cured. The adhesive 111 primarily used is an instantaneous adhesive, or adhesive primer and anaerobic adhesive, and is selectively used depending on the application, the object and the required strength.
However, the prior art has the following problems.
Namely, when the bonding with adhesive is made under an environment of a high temperature and a high humidity and the adhesive is completely cured in that environment, water content contained in the air adversely affects the bonding surface during the curing, so that the bonding strength is lowered. As a result, there will arise a possibility that the development sleeve is separated from the flange or it is driven in idle. Thus, the quality of the bonding is unstable.
Further, depending on the type of adhesive, a very long time may be required before the bond is completely cured. For this reason, a space to maintain it during that period is necessary, also the facilities to keep the maintenance environment temperature and humidity is required. Thus, these are disadvantageous in the aspects of cost, management and productivity.
Further, the development sleeve 103 and the development roller flange 104 are loosely fitted with a clearance and when the clearance is offset as shown in FIG. 8, a center offset between the development sleeve 103 and the flange 104 is given by A as shown in FIG. 8. Under this condition, when the rotational driving force is imparted to the photoconductor drum 101, the development roller is rotated by the photoconductor drum gear 102 through the development roller gear 108, so that the outer diameter of the flange 104 is moved with the vibration which is twice as large as the dimension A with reference to the outer diameter of the development sleeve 103. Accordingly, with reference to the surface of the photoconductor drum 101, the magnet roller 105 is moved by twice the dimension A per revolution. As a result, when viewed from the photoconductor drum, a magnetic force of the magnet roller is enhanced or deenhanced, so that the irregularity of density occurs on the image at the rotation period of the development roller.